This is the introduction of the catelogue. 
The keywords starting with "combined" originate from LAMOST; relevant documentation can be referenced at https://www.lamost.org/dr8/v2.0/doc/lr-data-production-description.
combined_obsid--Unique spectra ID in LAMOST dr8 low-resolution.
combined_class--Spectral type in LAMOST dr8 low-resolution.
combined_subclass--Stellar spectral type in LAMOST dr8 low-resolution.
combined_z--The value field shall contain a real floating-point number providing redshift for a target, which is determined mainly by the LAMOST spectra analysis pipeline. If the quality of a spectrum is poor, its redshift is artificially set to -9999 by LAMOST; however, in this paper, it is set to 0.
combined_ra--The value field shall contain a non-negative real floating-point number, which gives the right ascension of target from the input catalog. The data is sourced from LAMOST.
combined_dec --The value field shall contain a real floating-point number, which gives the declination of target from the input catalog. The data is sourced from LAMOST.
combined_rv--Heliocentric radial velocity obtained by the LASP.
combined_feh--Metallicity obtained by the LASP.
combined_logg--Surface gravity obtained by the LASP.
combined_teff--Effective temperature obtained by the minimum chi-squre estimation.
combined_file--The value field shall contain a character string giving the name of this FITS file. Take the “spec-58170-HD070403N361848V01_sp16-210.fits” as an example, “58170” is the local modified Julian day, “HD070403N361848V01” is the plan ID, “sp16” is the spectrograph ID, and “210” is the Fiber ID.
FeH--The estimated Metallicity in this paper.
CH--The estimated carbon abundance in this paper.
Teff--The estimated Effective temperature in this paper.
logg--The estimated Surface gravity in this paper.
CFe--The estimated [C/Fe] in this paper.
EGP--The EGP index calculated based on the LAMOST DR8 low-resolution spectra.
recommend_1--The spectral quality provided by LAMOST DR8 low-resolution is indicated, with a value of 1 representing good quality.
recommend_2--The EGP index shows a strong correlation with [Fe/H] and [C/H] in the range where 1 represents the spectra in that range.
recommend_3--Samples where the error in the EGP index calculated based on [Fe/H] is within one sigma, with 1 indicating a recommended selection.
recommend_4--Samples where the error in the EGP index calculated based on [C/H] is within one sigma, with 1 indicating a recommended selection.
recommend--Considering the recommendations from recommend_1, recommend_2, recommend_3, and recommend_4. It is recommended to use samples with values greater than 1 in this column.